\(A=\frac{3}{1\times4}+\frac{3}{4\times7}+\frac{3}{7\times10}+....+\frac{3}{197\times200}\)
\(A=\frac{1}{1\times4}+\frac{1}{4\times7}+\frac{1}{7\times10}+.....+\frac{1}{197\times200}\)
\(A=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+....\frac{1}{197}-\frac{1}{200}\)
\(A=\frac{1}{1}-\frac{1}{200}\)
\(A=\frac{199}{200}\)
a = 1/1- 1 /197 - 1 /200
a = 1/1 - 1/200
a = 199/200
\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+........+\frac{3}{197.200}\)
\(=\frac{1}{3}\left(3-\frac{3}{4}+\frac{3}{4}-\frac{3}{7}+\frac{3}{7}-\frac{3}{10}+...+\frac{3}{197}-\frac{3}{200}\right)\)
\(=\frac{1}{3}\left(3-\frac{3}{200}\right)\)
\(=\frac{1}{3}.\frac{597}{200}\)
\(=\frac{199}{200}=0,995\)
MINH LAM CHI TIET LAM DAY . MET LAM
CHUC BAN HOC GIOI NEU DUNG TK GIUP MINH NHA
